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Diesels: What’s all the clatter about?

Why now? Why twenty years after we, as a country, have lost interest in the slow, smoky Mercedes and Volkswagens that became synonymous with Diesel power? You can thank your government.

See, for years, residents living in countries with less than fifty states have been enjoying the fuel economy benefit of diesel passenger cars – they consume on average about thirty percent less than comparably powerful gasoline models – while we lumbered along in our thirsty, gasoline-powered SUVs. The reason we didn’t get the miserly diesels is simple: the quality of the diesel fuel available in this country was too poor to run the new engines on.

The new-technology diesel engines operate quietly and efficiently by injecting the fuel into the cylinders at ungodly high pressures through teensy nozzles. A high concentration of sulfur, which must otherwise be refined out of the diesel fuel, clogs those injectors.

For years, automakers and fuel companies have been stuck in a “you first!” battle like something you remember from grade school. “You refine the diesel fuel first, and we’ll bring the good engines in!” “No! You bring in the engines first, and then we’ll supply fuel for them! You first!” “No, you!”

Beginning in 2006, though, new regulations required that the fuel companies supply ultra-low sulfur diesel to the public. (Just in time, as it turned out, for the few remaining diesel passenger cars on the market to no longer be able to satisfy emissions regulations – but that’s another story). And so the floodgate opens, letting all the diesels in.

Aren’t diesels slow?

How about this for an answer: I lost a race in the new 414-hp, V-8 M3 last week to a diesel. I pulled up to a red light next to my photographer’s six-cylinder, automatic-transmission 530d station wagon. When the light turned green, I dumped the clutch from 2000 rpm and floored it. And the automatic diesel station wagon dusted my M3 off the line. I didn’t catch up until 60 mph.

Are diesels slow? That’s the same thing as asking if gasoline-powered cars are fast: Some are, some aren’t. Today, diesels make just as much power as comparably sized normally aspirated gas engines. Diesels make loads more torque, though, so they feel even faster than they are.

Don’t diesels smoke?

Not any more. Smoke coming from a diesel engine is partially unburned fuel, and the new engines run so efficiently they make sure there’s no waste.

Aren’t diesels hard to start in the winter?

Not any more. Well, to a point. Modern diesels don’t use glow plugs the way the old ones did – at temperatures above, say, 50F, they start normally. In temperatures below that point, they may take a couple of seconds extra to start – but not the minutes the old ones took.

The caveat is that diesel fuel turns into a Jell-O-like substance when it gets very cold. Modern fuels are treated with anti-gelling agents to prevent this, but they only work until a point. That point, however, is usually somewhere on the shivery side of -20F. So unless you live somewhere where it’s regularly colder than that, you needn’t worry.

Are diesels still more reliable – and longer-lasting – than gas engines?

Well, diesel engines aren’t really inherently longer-lasting than gas engines. Our experience with diesels in this country is generally limited to Volkswagen and Mercedes diesel engines, both of which were built to last until the End of the World. It wasn’t uncommon to see a half-million miles from those engines, but it also wasn’t unheard of to see a half-million miles from a contemporary gasoline-powered Merc or VW, either.

While it’s true that diesels still don’t have spark plugs, they have most of the other expensive stuff on them that their gas-powered siblings do. We expect them to be just as reliable as gas engines – which is to say very.

Why would I want a diesel instead of a hybrid?

That’s a really simple question with a really simple answer: Because if you want to save money, you don’t want a hybrid. Studies have shown that people are buying hybrid cars to send a message – not to save money. This is a good thing, because while they do save a little bit of fuel, they don’t save money.

Many hybrids will never save enough fuel to cover their initial cost premium, not to mention that the battery pack will some day need to be replaced at a huge cost.

Diesel cars also tend to have far better resale values than their gas-powered equivalents. For example, a 50,000-mile 2004 Volkswagen Jetta GL with a 115-hp gas engine is worth $8875 at auction. That same car with the same mileage, but a 90-hp diesel engine is worth $13,950. That’s $5075 – or 57% more. (The Touareg V-10 TDI’s resale value is even more impressive – see the chart below.)

It’s the same story for heavy-duty diesel trucks. A recent marketing study showed that after four and a half years of ownership, the average diesel truck is worth $4700 more than its gas equivalent, and has saved the owner more than $4200 in fuel. That $8900 difference more than offsets the truck’s astronomical initial purchase premium (an average of $6600).

To boot, diesels get their best fuel economy under the types of conditions that most Americans drive – on the open road. Automobile Magazine editor-in-chief Gavin Conway recently got nearly 40 mpg driving across Florida in a Mercedes E-Class diesel (a car that gives a Volkswagen GTI a run for its money in a stoplight drag). Hybrid systems offer almost no benefit on the highway, so unless you’re sitting in traffic, you’re not saving anything.

What about E85?

Do yourself a big favor and forget about E85. Much like Paris Hilton’s career, it’s made of a lot of hype and not a lot of substance.

You’d need 1.7 gallons of E85 to equal the energy contained in a gallon of diesel fuel. It takes something like seven percent more energy to create a gallon of ethanol than that gallon even contains. And to add insult to injury, if it weren’t for the federal and state tax breaks on E85, it would cost one dollar per gallon more than gasoline. (And that gallon of gasoline would contain 11.5% more energy, anyway.)

The E85 push benefits the car companies, not consumers. It gives the manufacturers a fuel economy CAFE credit for reducing gasoline consumption, even if the car is never run on E85. Which, of course, most never are. When was the last time you filled up with E85?

What’s with the urine?

None of the diesels currently available in the U.S. use urea injection – they all pass our current emissions standards without it. However, urea injection may be necessary in order to meet future emissions standards – especially for bigger cars. If so, it may be required to fill a small tank with colorless, odorless liquid about every other oil change, or 10,000 miles. And no, you can’t just pee in the tank.

Are diesels fun?

The way diesels deliver power is a lot like old-school American V-8 engines – loads of torque down low, and not much power at high rpms. In fact, diesels can’t rev faster than about 5000 rpm. (They can, physically, but they don’t make any power, because the piston is moving faster than the explosion in the combustion chamber, since diesel burns very slowly.)

So diesels are fun in the same way big-block, pushrod engines are – they’re fast off the line, and passing requires a stab of the right foot, not a four-gear downshift and 7000 rpm.

What do TDI, CDI, and Bluetec mean?

Bluetec is a brand name, like Kleenex or Xerox. It represents a joint effort between Volkswagen, Mercedes, and Chrysler to develop diesel engines that pass U.S. emissions standards.

Contrary to popular belief, Bluetec doesn’t insinuate the use of urea. The Bluetec companies plan on calling their urea additive “AdBlue.” Volkswagen is planning on calling their new diesels “Clean Diesels”.

TDI is a trademarked name that Volkswagen has given its diesel injections – it stands for Turbo Direct Injection, and describes the technology that injects the diesel fuel under high pressure directly into the cylinder, which has been force-fed with pressurized air from the turbocharger. In short, TDI is pretty much synonymous with “turbodiesel.”

CDI is the term that Mercedes uses for their diesels – it stands for Common-rail Diesel Injection – and which use the same high-pressure injection technology. CRD is Chrysler’s version – Common Rail Diesel.

Is this diesel technology experimental?

Nope. Forty percent of BMWs sold worldwide have diesel engines. In France, eighty percent of Audis are sold with diesel engines. The U.S. is late coming to a party that’s been going on for over ten years.

Where do I get one?

We’ve compiled lists of the cars you can get right now with a diesel engine – and asked everyone we could find to tell us what’s coming in the future. Some environmental experts are urging people to check their tire pressures so that they can save five percent on fuel economy. How about saving thirty percent? Stay tuned, because the diesel revolution is about to happen in America.

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